Kuiper David S, Douthwaite Richard E, Mayol Ana-Rita, Wolczanski Peter T, Lobkovsky Emil B, Cundari Thomas R, Lam Oanh P, Meyer Karsten
Department of Chemistry & Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, USA.
Inorg Chem. 2008 Aug 18;47(16):7139-53. doi: 10.1021/ic800139c. Epub 2008 Jul 15.
Treatment of trans-(Et 2O) 2MoCl 4 with 2 or 3 equiv of Na(silox) (i.e., NaOSi (t) Bu 3) afforded (silox) 3MoCl 2 ( 1-Mo) or (silox) 3MoCl ( 2-Mo). Purification of 2-Mo was accomplished via addition of PMe 3 to precipitate (silox) 3ClMoPMe 3 ( 2-MoPMe 3), followed by thermolysis to remove phosphine. Use of MoCl 3(THF) 3 with various amounts of Na(silox) produced (silox) 2ClMoMoCl(silox) 2 ( 3-Mo). Alkylation of 2-Mo with MeMgBr or EtMgBr afforded (silox) 3MoR (R = Me, 2-MoMe; Et, 2-MoEt). 2-MoEt was also synthesized from C 2H 4 and (silox) 3MoH, which was prepared from 2-Mo and NaBEt 3H. Thermolysis of WCl 6 with HOSi ( t )Bu 3 afforded (silox) 2WCl 4 ( 4-W), and sequential treatment of 4-W with Na/Hg and Na(silox) provided (silox) 3WCl 2 ( 1-W, tbp, X-ray), which was alternatively prepared from trans-(Et 2S) 2WCl 4 and 3 equiv of Tl(silox). Na/Hg reduction of 1-W generated (silox) 3WCl ( 2-W). Alkylation of 2-W with MeMgBr produced (silox) 3WMe ( 2-WMe), which dehydrogenated to (silox) 3WCH ( 6-W) with Delta H (double dagger) = 14.9(9) kcal/mol and Delta S (double dagger) = -26(2) eu. Magnetism and structural studies revealed that 2-Mo and 2-MoEt have triplet ground states (GS) and distorted trigonal monopyramid (tmp) and tmp structures, respectively. In contrast, 2-W and 2-WMe possess squashed-T d (distorted square planar) structures, and the former has a singlet GS. Quantum mechanics/molecular mechanics studies of the S = 0 and S = 1 states for full models of 2-Mo, 2-MoEt, 2-W, and 2-WMe corroborate the experimental findings and are consistent with the greater nd z (2) /( n + 1)s mixing in the third-row transition-metal species being the dominant feature in determining the structural disparity between molybdenum and tungsten.
用2或3当量的Na(silox)（即NaOSi(t)Bu₃）处理反式-(Et₂O)₂MoCl₄，得到(silox)₃MoCl₂（1-Mo）或(silox)₃MoCl（2-Mo）。2-Mo的纯化是通过加入PMe₃使(silox)₃ClMoPMe₃（2-MoPMe₃）沉淀，然后热解以除去膦来完成的。使用MoCl₃(THF)₃和不同量的Na(silox)生成了(silox)₂ClMoMoCl(silox)₂（3-Mo）。用MeMgBr或EtMgBr对2-Mo进行烷基化反应，得到(silox)₃MoR（R = Me，2-MoMe；Et，2-MoEt）。2-MoEt也可由乙烯和(silox)₃MoH合成，而(silox)₃MoH是由2-Mo和NaBEt₃H制备的。用HOSi(t)Bu₃对WCl₆进行热解得到(silox)₂WCl₄（4-W），4-W依次用Na/Hg和Na(silox)处理得到(silox)₃WCl₂（1-W，三角双锥，X射线结构），也可由反式-(Et₂S)₂WCl₄和3当量的Tl(silox)制备。用Na/Hg还原1-W生成(silox)₃WCl（2-W）。用MeMgBr对2-W进行烷基化反应生成(silox)₃WMe（2-WMe），其脱氢生成(silox)₃WCH（6-W），活化能垒ΔH（双匕首）= 14.9(9) kcal/mol，熵变ΔS（双匕首）= -26(2) eu。磁性和结构研究表明，2-Mo和2-MoEt分别具有三重态基态（GS）以及扭曲的三角单锥（tmp）和tmp结构。相比之下，2-W和2-WMe具有压扁的Td（扭曲的正方形平面）结构，前者具有单重态GS。对2-Mo、2-MoEt、2-W和2-WMe的完整模型的S = 0和S = 1态进行量子力学/分子力学研究，证实了实验结果，并且与第三行过渡金属物种中更大的ndz²/(n + 1)s混合是决定钼和钨之间结构差异的主要特征这一观点一致。
